US2197155A - Screw mechanism - Google Patents

Description

April 16, 1940.

R. M. NARDQNE SCREW MECHANISM Filed Sept. 10, 19258 2 Sheets-Sheet l Kik..

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April 16, 1940. R. M. NARDONE scREw MEcHANIsu Filed sept. 10. 19s8'f 2 Snets-sheet 2 Imm! INVENTOR NEY.

tl', I IIII Patented Apr. 16,

UNITED STATES PATENT OFFICE i `2,197,155 .I 'l n SCREW MECHANISM ltomeo-M. Nardone, East Orange, N. J., assignor to Bendix Aviation Corporation, South Bend, Ind.; a corporation of Delaware v i* l Application September 10, 1938, Serial No. 229,376` y i s claims. (ci. 'a4-459) This invention relates to driving mechanism, and more particularly to driving mechanism of the class employing substantially frictionless rollers-balls, cylinders, or other rollers having curved rolling surfaces-in positions intermediate the driving and driven elements, for transfer of the drive from one to the other, in conjunction with a retaining cage or cages for said rollers.

An object of the invention is to provide novel means engageable with certain of the rollers to absorb thrust, facilitate free rolling,. and limit axial movement of the roller assembly, particularly in cases wherein the roller assembly is interposed between driving and driven elements ll adapted to translate longitudinal motion to rectilinear motion, or vice versa.

These and other objects of the invention will become apparent from inspection of the following specification when read with reference to the acn companyingdrawings wherein is illustrated the preferred embodiment of the invention. It is to be expressly understood, however, that the drawings are for the purpose of illustration only, and are not designed as a deiinition of the limits s of the invention, reference being had to the appended claims for this purpose.

In the drawings,

Fig. 1 is a longitudinal sectional view of the invention as applied to screw mechanism for .0 starting an internal combustion engine, the starting mechanism shown being that which is dis- ;'closed and claimed in my application No. 100,000 filed September 9, 1936, now patent No. 2,144,196 granted January 17, 1939;

Fig. 2 is a transverse sectional view along the line 2-2 of Fig. 1;

Fig. 3 is a side elevational view of an element of the assembly of Fig. l;

Fig. 4 is a longitudinal sectional view of certain 0 of the parts of Fig. l, butin different relative 'postions;

Fig. 5 is a detail view of the cage balls and stops assembly on an enlarged scale;

Fig. 6 is a longitudinal sectional view of a 45 portion of the motion translating means of Fig. 1, incorporating therein a modified arrangement for retaining and controlling the action of the m0- iion facilitating ball elements carried by said motion translating means;

50 Fig. '7 is a'transverse section along the line 1-1 of Fig. 6;

Fig. 8 is an exploded perspective view of the inner cag: in non-assembled relation to certain ofthe driving elements; and

55 Flgs..9 to 12, inclusive, are diagrams illustrating 4successive stages of theroller and cage assem? bly process, for the embodiment of Fig. 6. l

With reference to the drawings, and more 'particularly to Fig. 1, the screw mechanism is contained within a sectional housing including cylin- 5 drical parts l1 and i0, the latter having a flange i2 by which it is secured tor an engine crankcase i3 as by bolts Il, the flange being conveniently of a size standardizedfor aircraft engine starters. The engine crankshaft, or other drive shaft l0 (not shown) is provided with a clutch-element I I engageable by the piston actuated clutch-element` i5 as will be later more fully described.

Cylinder I1 has a head end I3 and a crank end 20, the latter being shownas an integral ll part of a splined tube 2l. Slidably fitted within the cylinder I1 is a piston 23 movable with a hollow internally and helically grooved screw 24 which is externally splined as at 25, to cooperate with the internally splined tube 2 I. Between the m cooperating grooves 25 and 26 are placed a series of friction reducing members shown as balls 21 assembled in a cylindrical cage a (Fig. 5), the end rows of balls having their surfaces engageable with plates 28 located at each end of the 25 splined grooves to facilitatefree rolling movement of the balls which they engage at points spaced above or below the mid-plane thereof, and also to hold thecage 30a against more' than a predetermined e'ndwise movement. A'second 30 screw 22 is drivably connected with the screw 2l by helical grooves or threads 29 and 30 which permit the axial travel of the piston 23 but cause rotation of the screw 22 because of friction reducing balls 36 inserted in the helical grooves 35 29 and 30. An anti-friction thrust bearing 32 is preferably interposed between a flanged skirt 34 on rear end of spacer 34a and an inwardly extending circular rim 33 of the cylindrical part I0. The inwardly extending rim 34h on the forward 40 end of spacer 34a takes the thrust as jaw i5"` rides into mesh with engine member ii. A spring 31 has one end resting against the closure plate 2li of the cylinder i1, and its opposite end abuts the thrust ring 38, which is, in effect, the outer race of a ball bearing assembly i0 axially movable with but rotatably free of the piston 23, the intervening bearing balls 40 facilitating free rotation of outer race 38 of the bearing, the outer race being possibly constrained to rotation by the natural twisting tendency of a spring such *as the spring 31, as the latter is compressed in'the forward travel of the piston. Piston rings, insure against the loss of pressure as the piston moves forward, and also yieldably oppose rotation a vio 2 arcaica haust connection 4i leading to any desired point.

In the case of an airplane. for example, this exhaust connection will lead to a point exteriorly of the fuselage. 'I'he valve 42 is carried by a stem ll whichis of such a length that with the piston' in its position as indicated in Figure l. a spring Il will bear against an enlarged head I! on the stem 4l to hold valve Il closed. At the commencement of an operative cycle of the motor, such asis occasioned by the delivery of fluid pressure to the chamber formed by the neckportion I8 oi' the housing Il, this fluid pressure will act upon the head portion of the valve insuchmannerastoassistthespringin maintaining `the said exhaust valve l2 allied:

but as the piston nearly reaches the end of its zmovement. a collar extending inwardly of piston 2l and surrounding the stem will be brought into engagement with the head l2 and, will be edective to unseat the exhaust valve 42. 'I'he exhaust valve having been unseated in the manner described, the spring 48 will be en'ective for holding it in open position, its maximum opening movement being limited by a longitudiy nally slotted cylindrical stop Il having a flange t8 abutting the end surfaces oi' the nngers Il (shown in transverse section of Fig. 2) formed by longitudinally slotting the neck portion Il of the housing I8. I'his neck-portion 8l is externally.

threaded, as shown at n, to receive the housing M. the latter being screwed up on the threads 68 until surface I0 of the housing u abuts the.

flange B6 of the stop N and with the inlet passage lia aligned with the longitudinal slots between ilngers 81. Stop u is adapted-to be first slipped over the valve head 42: and due to the eccentricity (indicated at Il in Fig. 2) of the apertured portion of the base 'Il of the said stop, the said base has suiilcient surface remaining to constitute a 'stop or abutment for valve head l2 in the open position of the latter, while at the same time being apertured suiiiciently to permit insertion and withdrawal over said valve head.

'I'he piston having completed its operative stroke. and the exhaust valve having been opened. the piston will be urged on its return stroke by the coil spring Il. During this return movement, the exhaust valve being held open, the cylinder will be effectively scavenged.' Due to the action of the spring the valve will remain open until such time as the piston odiar Il is brought to bear against the valve stem 41 for again seating the valve. This insures closing movement of the valve at the time the piston has substantially completed its return movement. the

closing being initiated and assisted by the action of the spring means l! above described. There is thus provided automatically controlled exhaust means, which exhaust means is of such construction as to remain open during the maior portion of the return stroke of the piston so as to insure substantially complete scavenging.

"15." By reason of the action oi' sprinpm nu,

Il `and Il upon grooves Il and Il. respectively in sleeve 22.' the initial axial movement of the piston 28 will be transmitted toeaid sleeve l2, and theaxialthrustthusimparted toiaw Il (through the flange I! on sleeve l!) will establish engage I ment with the engine member Il. Upon such engagement the resulting resistance to further i axial travel will cause, nrst, al commencement of rotation on the part of sleeve 22, and secondly, a slipping of the balls Il and Il from the grooves il)v f 4Il and Il, so that they may be free to ride along the inner bore of the sleeve 21 as the piston continues forward; the furthest forward relative position of the balls "and Il being as indicated In order to assure alignment between the longitudinal slots IIb in the thimble shaped stop Il, and those'slots I'Ia formed by the lingers i1 of the neck portion Il, iiat surfaces Ma are provided on the :nimble shaped stop (as indicated in both 1 vFigures2itndli)toreg'isterwithcorresponding.-

flat surfaces lia on neck portion il. Thus there -is established a direct path for the pressure fluid entering the housing, said path being in the form or a plurality orparsnel passages straight c through the lower halves ,of the slotted cylindrical walls of neck portion `It and thimble shaped stop Il, the said parallel passages being sumciently numerous and wide to allow entry of 'all the non-solid part of the charge, while narx 0.

row .enough to block entry of any solid (unburned) pellets or particles of explosive material from which the pressure iluid may be generated.

If the entering fluid attains an' excessive preesure or velocity,'suilicient to carry it `thro'ugh o5 the upper slotted sections oi' thimble shaped stop I4 and neck` portion Il, with such abnormal force as to rupture the protective disc l0, the

'breaking oi' said disc .will permit the escape to I the atmosphere, by way of outlet of such excess pressure, thereby protecting the other parts of the device against derangement; but normally the advance of piston 2l (in response to the entry of the nuid into the chamber formed by the neck-portion it) will be rapid enough i to prevent accumulation of excess pressure in the crescent shaped region 'la immediately above the neck-portion 56. This region 1l is formed by making the inner surface of housing Il elliptical in cross-section, atthe parts (1l and 11) 50 above and below the threaded regions (13 and 14) of contact with the threaded surfaces 'Il of the neck-portion Il. This has the added advantage of providing a greater 'width of inlet space at region 1l (Fig. 2), making it possible 55 to' utilize all of the parallel passagesforlned by fingers l1.

In the arrangement shown in Fig. 6 retainer rings 2l, Il and II are secured 'to the ends of elements 2|, 24 and 22, respectively, and engage $0 the end rows of the balls 21V and 3l in tangential fashion rather than the edges of the cages, so that theytend to insure free rolling of the said balls, where otherwise there mightbe a binding or wedging tendency-as, for example, if the ,65 retainer surfaces engaged the balls at points in the surface of a cone passing through the centers of said balls, with its apex on the llongitudinal axis of the sleeves Il, 24 and 22.

To vassemble the Darts. I ilrst stand the sleeve 70 .Il on end, as best shown in Fig. 8, and after placing cage l2 and retainer ring ll over the shaft of sleeve 24. With the parts in this position I then proceed to insert balls 88 in the said lowest row 81 of openings, the said openings being sui!!- ciently exposed to permit such insertion, and the concave surfaces of the threads 88 at the upper end of sleeve 24 form shoulders to prevent dropping out of the balls during the process oi illling this row of holes 81. When the openings in row 81 have been thus illled, vI apply pressure on the shaft 22 to move it down, in relation to vsleeve 24, a distance corresponding to the distance between transverse rows (the distance indicated at din Fig. 8). I then proceed to rlll the row 88 with balls, and the concave surfaces of the threads 38 at the upper end of sleeve 24 again aid in the retention of the balls against dropping out during this step in the process. These steps offllling one transverse row at a time, then telescoping the inner shaft or sleeve 22 to an extent equal to the distance between rows, are repeated, until the cage has been completely illled with balls, as shown in Figs. 6 and 1, and completely telescoped within the sleeve 24. Retainer ring 84 is then secured over the end oi sleeve 24, the lip 88 of said retainer ring being registrable with an undercut recess in the splines 28 of the sleeve. The assembled shaft and sleeve are then inverted and placed above the outer sleeve 2 I, the latter standing on end on a suitable support.` Gage 8| is then slid over the end of sleeve 24, down to the point where the lowest row of openings therein will be adjacent the plane of the end of the sleeve 24, as shown in Fig. 9. I then proceed to fill the rows with balls 21, one row at a time, with each successive step of row lling separated by a step of telescoping the sleeves 24, 2l to an extent equal to the distance d' between successive rows, in other words, a repetition of the steps followed in assembling the parts 22, 82 and 24, as previously describedthe successive steps being indicated in Figs. 10, 11 and 12. When this has been completed, re-

tainer ring 28 is secured in place to complete the entire assembly. v

What is claimed is:

1. The combination with two cylindrical drive transmitting parts, of a cylindrical roller retaining cage interposed therebetween, a plurality of rollers in said cage, and a retainer plate secured to one of said drive transmitting parts, said plate having a surface engageable with points on said rollers which are on parallel lines each of which passes through the center of onel of said rollers, and each of which passes through the cylindrical wall of said cage.

2. The combination with two cylindrical drive transmitting parts, of a cylindrical roller retaining cage interposed therebetween, a plurality of rollers in said cage, and a retainer plate secured to one of said drive transmitting parts, said plate having a surface engageable with said rollers tangentially thereto.

3. The combination with two cylindrical drive transmitting parts, of a cylindrical roller retaining cage interposed therebetween, a plurality of rollers in said cage, and a retainer plate distinct from said cage and secured to one of said drive transmitting parts, said plate having a surface engageable with said rollers to limit the motion of said cage in relation to said drive transmitting parts.

ROMEOl M. NARDONE.

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